The utility of electric submersible pumps (ESPs) is sometimes limited by conventional deployment and retrieval methods. A conventional ESP may be installed with a tubing string, requiring a full rig to perform the work. Such installations can be costly, particularly in offshore and remote locations, frequently making ESP installations and retrievals economically prohibitive. As such, a desirable deployment method would avoid the need for a rig and allow the assembled ESP system to be “stripped” into the well through-tubing. Coiled-tubing and cable deployed ESPs have been developed that meet these requirements, but they still have limitations.
The most flexible commercially available coiled-tubing-deployed system employs an internally-installed cable. The cable used is pumped into the coiled tubing, with 10,000 feet the greatest length that vendors have been able to install. A three-phase, No. 2 AWG cable inside of 1¾″ coiled tubing represents a typical application. The cable may or may not be anchored inside the coiled tubing, and thermal expansion/contraction effects may be a concern. As may be appreciated, the cable-in-coiled-tubing reel is quite heavy, and lifting operations can challenge offshore cranes; certain platforms may require a support barge for installation. The system cannot easily be spliced, which means the entire string can be lost if there is an issue. Spooling and straightening of the reel can weaken or damage the cable and limit re-use.
Despite these advances, what is needed are improved systems and methods for deploying and powering an electric submersible pump within a subterranean well, which enable deployment at depths greater than about 10,000 feet.